ListView needs an IComparer to be assigned to the ListViewItemSorter property, for the sorting work. Read the help on the Sort property on MSDN for a sample, if your class already implements IComparable, you can simply delegate it to the CompareTo() method, and code the IComparer with one line of code only. And that, IMO is a design mistake, and should be done by the ListView by default. Yes, even I am blogging now!

I use TCP Client class in the C# client program to connect to the server. I use the accept method in the c-written server to accept the incoming socket connection.

Drag and drop registration must be performed on the STA thread, so it must be called from the thread on which the control was created. If you're setting the AllowDrop property from a different thread, use Invoke for that as well, getting the get accessor using Reflection and creating a delegate that matches the signature. Call Control.Invoke using that delegate that references the get accessor method. Microsoft MVP, Visual C# My Articles

Form1 is what the message pump is using to keep the loop alive so that it translates and dispatches messages throughout your application (Windows Forms just encapsulates Windows messaging and common controls). Disposing your form (or even closing it) stops the message pump. If you're desiging a wizard-like interface, you should consider having a single form that maintains state between forms as well as navigation between them. And instead of Form derivatives, you could actually use any container control such as a UserControl (easiest to design in VS.NET, if you like that sort of thing). There are several articles here on CodeProject that discuss this. If you want to create a new main window for your application, then you could try using Application.Run on your instance of Form2 then dispose Form1. I'm not sure how this would affect your application, however, since a new STA thread would be created for the new main window. Give it a try, though. Microsoft MVP, Visual C# My Articles

The way you're doing it is not optimal and often leads to problems because certain characters - like quotes - are not escaped properly. See the documentation for the OleDbParameter class and use a paramterized query like so: OleDbCommand cmd = myConnection.CreateCommand(); cmd.CommandText = "UPDATE userinfo SET Password=? WHERE " + "Name=? AND Password=?"; cmd.Parameters.Add("NewPassword", OleDbType.VarWChar, 40).Value = newPassword; cmd.Parameters.Add("Name", OleDbType.VarWChar, 40).Value = user.Name; cmd.Parameters.Add("OlePassword", OleDbType.VarWChar, 40).Value = oldPassword; int i = cmd.ExecuteNonQuery(); Console.WriteLine("{0} record(s) modified", i); The OLE DB provider for ADO.NET does not use named parameters, and instead uses positional parameters using the question mark, so you must add your parameters in the same order. The example aboves assumes you declare your fields as Text using 40 characters as the length. This is just an example, though, so read the documentation for the OleDbParameter for more information. Microsoft MVP, Visual C# My Articles

The threads you have created may be foreground threads. These threads will keep the process running until they stop. Try setting the Thread.IsBackground property to true. Once all foreground threads have stopped executing the runtime will abort all background threads automatically.